Brittany Ferries are pet-friendly, even for cats. On some routes, you can even book a cabin where your dog gets greeted with a water bowl, a toy, treats and waste bags. Other ships have kennel areas, but for shorter sailings, there's an option to have your dog sit with you as long as a member of the staff can hang out too. Truth be told, France is accommodating and the French people love dogs. But the country's laws are what you have to work around and one must respect everyone's comfort with dogs.
Located on the coast of the English Channel, at the mouth of the river Dives, Cabourg is a gorgeous place to just have a beach day. Pack up some cheeses and wine, bring a blanket, and call it a day. Dogs are allowed on a leash in front of the sand dunes, on the Pointe Sauvage, and after Cap Cabourg.